The latest evidence came Wednesday, when Nuclear Regulatory Commission Chairman Gregory B. Jaczko testified before the House Energy Committee that, if this accident were taking place on American soil, his agency would evacuate residents within 50 miles of the plant, more than twice the distance Japanese authorities have used to define their evacuation zone.

Why, anyway, were critical backup systems exposed to the effects of tsunamis in a country that coined the term for those relentless surges of water? A country that sits astride the sort of massive, deep fault that produces earthquakes far larger than those in California? This was not some unknown danger.

It became clear in Jaczko's questioning Wednesday that backup diesel generators at American plants facing risk of storm surge or hurricanes are generally much better protected than those at Fukushima Daiichi. In fact, American regulators, stricter since Three Mile Island, require that nuclear plant operators build safeguards against any natural disaster in the historical record of the sites on which they build, and that they include a margin for error and the unexpected.

The Japanese, to be sure, are not reckless, as the Soviets were during Chernobyl. Nuclear power will always pose its dangers, though the odds of disaster are still exceptionally small. And no regulator or utility is perfect, in Japan or in America. But folks who live next to nuclear power plants don’t necessarily face the same level of risk those around Fukushima Daiichi did.